Electro-fluid transducer



March 28, 1967 R. N. GOTTRON 3,311,122

ELECTRO-FLUID TRANSDUCER Filed Jan. 15, 1964 2 Sheets-Sheet 2 /N VEN TOE, /Z/CH/JED A/ 6077/?0/V United States Patent Oflfice 3,3 1 1,122 Patented Mar. 28, 1967 3,311,122 ELECTRO-FLUlD TRANSDUCER Richard N. Gottron, Kensington, Md, assignor to the United States of America as represented by the ecretary of the Army Filed Jan. 13, 1964, Ser. No. 337,568 6 Claims. (Cl. 137-815) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment to me of any royalty thereon.

This invention relates to controlled fluid jet devices, and more particularly to acoustically controlled bi-stable fluid jet devices.

The concept of Fluid Amplification has led to the development of radically new fluid components and systems, and these developments have themselves created new problems tnd generated new needs. Today, many systems are characterized by having electrical, mechanical, and fluid operable components which are functionally interrelated. For these and other applications a need has been recognized for a hybrid fluid device which can translate electrical information signals directly into fluid signals. Several solutions have been suggested and attempted, but have not been completely successful. Primarily, they lack the simplicity, compactness, and reliability characteristic of Fluid Amplifiers.

The broad object of this invention is, therefore, to provide a novel fluid jet device which is simple, compact, and reliable, and which can translate non-fluid information signals into a fluid jet position output signal. This broad object of the invention is accomplished by means of acoustic control. The most common application of this invention contemplates the translation of an electrical signal into an acoustic signal which is applied to a fluid jet to control its position. Transducers to convert electrical or mechanical information signals into acoustic signals are highly developed items; compact, reliable, and relatively inexpensive. Two very common transducers are the electromagnetic type, and the piezoelectric crystal. Both are suitable for use in the practice of this invention.

Another broad object of this invention is to provide a fluid device which can directly utilize a high frequency input signal to position control a fluid jet. This object, as will become more apparent subsequently, is also accomplished by means of acoustic control.

There are additional subsidiary objects of this invention directed more specifically to acoustic controlled fluid devices. One such object is efficiency. That is, achieving fast, reliable control of a fluid jet with low input energy to the acoustic transducer.

Another object of this invention is to be able to use several different acoustic drivers and transducers, and locate them at various points relative to the fluid jet. This flexibility permits various control characteristics, as

well as allowing freedom to choose a geometry which best meets the space requirements of the system.

An additional object of this invention is to provide an acoustically controlled fluid logic element.

As will become apparent to those skilled in the art, the instant invention makes use of certain concepts developed in connection with fluid amplifiers, and more particularly with that class of fluid amplfiiers known as the bi-stable or flip-flop type. Details of this type of fluid amplifier may be found in the co-pending application of Romald E. Bowles and Raymond W. Warren Ser. No. 58,188, filed Oct. 19, 1960. In common with bi-stable fluid amplifiers, this invention employs a fluid jet forming nozzle, a pair of fluid receiving apertures downstream from the jet nozzle, and a pair of oppositely diverging walls intermediate the apertures and the power jet nozzle onto which the power jet can lock. The position of the power jeti.e., the wall to which it is locked-is indicative of the condition of the device, and is responsive to an input information signal. In accordance with the teachings of this invention, the position of the fluid jet is controlled by means of an acoustic signal. An acoustic signal, as used in this application means a series of alternate positive and negative pressure waves traveling through a medium by wave propagation.

The specific nature of the invention, as well as other objects, aspects, uses and advantages thereof, will clearly appear from the following description and from the accompanying drawing, in which:

FIG. 1 is a plan view of one embodiment of an acoustically controlled fluid device constructed in accordance with the teachings of this invention.

FIG. 2 is a sectional view along the line 2-2 of FIG. 1.

FIG. .3 is a plan view of an alternate, preferred embodiment of this invention.

FIG. 4 is a plan view of an acoustically controlled AND logic unit.

FIG. 5 is a plan view of still another embodiment of the present invention.

FIG. 6 is a plan view of yet another embodiment of this invention.

FIG. 7 is a sectional view along the line 77 of FIG.

The principles of this invention will be described in connection with the embodiment of FIG. 1. Here, the reference numeral 10 indicates a confined, two dimensional bi-stable fluid jet device. This device 10 is of the wall lock-on type utilizing the principle described in the aforementioned co-pending Bowles et al. application, and has a fluid jet forming nozzle 11 with an orifice 11a. Downstream from the nozzle 11 are a pair of fluid receiving apertures 12 and 13. Intermediate these apertures 12 and 13 and the power jet nozzle 11 are two lock-on walls 14 and 15. Intermediate the aperturess12 and 13 is a divider or splitter 16. The splitter, in conjunction with the fluid lock-on walls 14 and 15, forms a pair of fluid receiving channels 17 and 18.

The operation of the structure thus far described is: fluid power is applied at 19, a fluid jet is formed in the nozzle 11, the fluid jet impinges upon splitter 16, and although the device 10 is symmetrical about the nozzle orifice 11a, an initial turbulent condition about the splitter 16 will quickly cause the fluid jet to bend over and become attached either to the wall 14 or the wall 15. Attached to either of the lock-on walls, the fluid jet is in a stable condition, and substantially all of the fluid is captured either in the channel 17 or 18, and issues from orifice 12 or 13. The point where the fluid jet attaches to the fluid jet lock-on wall 14 or 15 is dependent upon the geometry of the device 10 and upon the fluid pressure developed at jet nozzle orifice 11a.

The fiuid jet locked-on and issuing from either the aperture 12 or 13 entrains fluid from the area between the power jet nozzle orifice 11a and the point of attachment to the lock-on walls 14 or 15. This entrainment forms a region of reduced pressure in the areas denominated 22 and 23, depending on the wall to which the jet is attached. It is this region of reduced pressure, sometimes called an entrainment bubble, which makes the power jet stable in its locked-on condition.

To control the position of the jet issuing from nozzle 11 applicant has provided two acoustic control mean-s 24 and 25, and acoustically conducting media 26 and 27 between the acoustic drivers 24 and 25 and the power jet issuing from nozzle 11. Suitable transducers for use vices. The acoustic transmission media 26 and 27 may, theoretically, consist'of material in any state, e.g. solid, liquid, or gas. However, in order to provide good coupling from the drivers to the media, and from the media to the jet, a fluid would be most suitable as a conducting medium. Normally, the fluid which forms the jet, and the fluid which forms the conducting medium will be the same type. Where the acoustic conducting medium is a fluid, the best coupling efficiency is usually obtained if the medium is contained within an exponential horn such as 28.

FIG. 2 shows the usual mode of construction for two dimensional fluid jet devices. The channels and nozzles shown in plan in FIG. 1 are usually etched, gouged, or

machined out of one block 31., and a second block 32 is tightly secured to the block 31 forming the channels, such as nozzle 11.

The operation of the acoustically controlled fluid jet device 10, shown in FIG. 1, is as follows. A fluid jet formed in nozzle 11, issuing from orifice :ijll, locks on to one of the walls 14 or 15. Assume for purposes of illustration that the power jet is initially locked-on to the wall 15 and that there is no acoustic signal from either the driver 24 or 215. An acoustic signal developed by transducer 25, conducted by acoustic transmission medium 27, causes the power jet to become detached from the wall 15, switch, and become attached to the opposite wall 14. This is the second stable state of the device 10. Similarly, with the power jet attached to the wall 14, an acoustic signal developed by the acoustic driver or transducer 24 causes the power jet to becomedetac-hed from the wall 14, switch, and become attached to the wall 15.

Of course, there is no appreciable net flow of the acoustic transmission medium caused by the transmission of and acoustic signalthe energy being transmitted by wave motion. Also, of course, it is impossible, as a practical matter, to obtain peak to peak pressure variations of the acoustic signal which are even close to the pressure required to switch the jet with transducers of reasonable size and frequency. This fact, that acoustic energy introduced into the separation bubbles formed in the regions 24 and 25 cause the power jet to switch, can be explained on the basis of radiation pressure.

Radiation pressure is, as is known in the art, a phenomenon similar to the radiation pressure developed :by light upon a surface. Sonic radiation pressure is the net increase in pressure exerted by sound waves upon any surface, reflectingor absorbing, on which the sound waves fall. In the normal derivation of the pressure of an acoustic wave, it is assumed that the density of the medium is unchanged from its equilibrium value. if the variation in density is taken into account, a second order is introduced for the pressure. The radiation pressure is time independent, and for a plane acoustic wave incident upon a perfect absorber is, for small amplitudes, the situation most nearly encountered in the practice of this inventiori), equal to:

P =l/ a where,

l5 is the radiation pressure, I is the acoustic intensity, a is the speed of wave propagation.

Negative local pressures on the order of 160 dynes/crn. have been achieved experimentally.

This is to say, that with the power jet in right hand channel 18, for example, there will be a reduced pressure area in the region 23-the so called separation bubble, This separation bubble is formed between the jet issuing from 11a and the reattachment point somewhere downstream on Wall 15. Now, when sound is introduced into this region, due to the radiation pressure, the pressure on the jet builds up, creating a force on the jet finally causing it to switch to the left offset wall 14.

However, this does not fully explain the observed operation. Another second order effect-acoustic streamingalso has an effect on the switching of the power jet. This acoustic streaming is believed responsible for the observed effect that the introduction of sound into the power jet causes tne reattachmeut point to move downstream. This downstream movement of the reattachrnent point causes the power jet to be less stable, since the power jet tends to impinge on the splitter.

An acoustic streaming concerns the phenomeon which has been observed in a closed tube in which sound has been injected at one end. The acoustic wave propagates along the tube with the normal periodic change in the medium parameters. Also, there is a one directional flow in me center of the tube in the direction of propagation, with a return flow along the sides of the tube. It is the acoustic streaming in the power jet itself with sound applied to the jet from the drivers 24 or 25, which is believed responsible for the shift of the reattachment point. The combination of these two effects-radiation pressure and acoustic streaming are responsible for the power jet switching to the opposite wall when a high frequency acoustic signal is applied by 24 or 25.

PEG. 3 illustrates a preferred specific embodiment of this invention. The fluid jet device 40 has a power jet nozzle 41, with an orifice 41a. Two power jet receiving channels 47 and 48 are defined, and separated by a splitter 46. The fluid jet device 40 thus far described is similar in construction and operation to that shown and described in connection with FIG. 1.

In this embodiment, the acoustic control means takes the form of a pair of piezoelectric crystals 44 and 45, and the crystals 44 and 45 actually form a section of the channels 4-7 and 48.

An alternating voltage applied across quartz crystals 44 and 45 will cause the crystals to vibrate and, if the frequency of the applied alternating voltage approximates a frequency at which mechanical resonance can exit in the crystals, the vibrations will be intense. These mechanical vibrations of the crystals 4-4 and 45 generate the acoustic signal which controls the position of the jet issuing from orifice 41a. The mechanism of operation is substantially the same as that described in connection with FIG. 1. in this embodiment, however, the acoustically conducting medium is the fluid which surrounds the jet in the entrainment bubble regions 42 and 43.

As can be seen from an inspection of FIG. 3, this embodiment is simple, compact, inexpensive, reliable, and rugged. There are no moving parts in the accepted sense of the termmerely vibrating crystals 44 and 45. Additionally, since the transducers 44 and 45 are inherently high frequency devices, a high frequency information signal may be applied directly to them to control the position of the power jet. This direct utilization permits the matching of a high frequency signal source to the inherently low frequency bi-stable fluid element.

lFIG. 4 is an AND unit, having two fluid receiving channels 57 and 58 separated by a splitter 56. In the hybrid logic element of FIG. 4, the splitter 56 is not symmetrical with respect to the jet forming nozzle 51, but is offset to the right a sufflcient amount so that the fluid jet will, in the absence of any input signal, lock-on to the left hand wall 54 Forming part or the left hand output channel 57 it is a piezoelectric transducer 54, powered by a signal source 54'. The left hand side of the fluid logic element shown in FIG. 4, with the exception of the offset splitter 56, is similar to the device shown in FIG. 3. However, the right-hand side of the fluid logic element shown in FIG. 4 is cut back away from the nozzle orifice in the region 5?; as shown. This prevents the fluid jet formed in nozzle 51 from attaching, and locking-on to the righthand wall when the how is out the right-hand channel 53.

The fluid input at 549 has been symbolically designated as A, and the acoustic signal input generated by piezoelectric crystal 54- is designated as B. An output from the left-hand channel 57 represents A not B, and an output from the right channel 5'8 represents an output A and B.

In operation, a fluid jet formed in nozzle 51 issuing from orifice 51a will, in the absence of an acoustic signal, attach to the left-hand wall 54 and flow from the channel 5'7. An acoustic signal developed by crystal 5% applied to the locked-on fluid jet causes the jet to become detached from the left-hand wall 54-, move toward, and flow from the right-hand output channel 58. The fluid jet does not attach to the right-hand wall of this channel, however, because of the cut back in the region 52. Therefore, because of the position of the splitter when the B signal is removed, the nuid output switches back to the left-hand channel 57. Obviously, therefore, the output in the righthand channel 58 represents the condition A and B, as previously mentioned.

The embodiments of FIGS. 5 and 6 are alike in that they make use of the acoustic streaming and radiation pressure eflect previously mentioned.

FIG. 5 shows an acoustically controlled fluid jet device 69, the output of which is used to control a proportional amplifier 61, shown schematically, and which may be of the type described in the co-pending application of Billy M. Horton, Ser. V0. 51,896, filed Sept. 19, 1960, now Patent No. 3,122,165. The fluid jet hybrid device 66 comprises a source of input fluid power 62 and a fluid jet forming nozzle 63 with an output orifice 63a. Downstream from fluid jet orifice 63a is a pair of receiving channels 65 and as separated by a splitter 64. The unit 68 is geometrically biased so that a fluid jet formed in nozzle 63 will attach to the left hand wall 67 of the left hand channel A portion of the right hand wall of the right hand channel 6-6 may be cut away in the region 68 in order to prevent the fluid jet from locking on to this wall. Upstream from the nozzle orifice and the nozzle 63 v is an acoustic transducer 69, which may be in the form of a piezoelectric crystal.

In the absence of a signal from acoustic transducer 69, the fluid jet formed by nozzle 63 and issuing from orifice 63a attaches to the wall 67 and issues from channel 65, creating a relatively high pressure in that channel. Although the fluid jet is locked on to the wall 67, due to the proximity of the leading edge or the splitter 64 to the nozzle orifice 63a, a relatively small amount or" fluid impinges upon the splitter 64 and flows out the channel 66, producing a low but appreciable pressure in this channel. The outputs of the channels 65 and 66 are applied to the proportional amplifier 61, and control the position of the fluid jet of the proportional amplhier in accordance with the differential pressure between channels 65 and 66. When an acoustic signal developed by transducer 69 is injected into the fluid stream upstream of the nozzle 63, the point of attachment of the jet to the wall 65 moves downstream, causing more fluid to impinge upon the splitter 64more fluid flows out of channel 66, and the pressure in this channel is thereby raised. This change in differential pressure between channels 65 and 66 is amplified in proportional amplifier 61.

As previously mentioned the mechanism by which the device as operates is believed to involve acoustic streaming in the nozzle 63 and nozzle orifice 6311. With the direction of acoustic propagation in the direction of fluid jet flow, the steady flow in the direction of propagation and the counter flow, both due to acoustic streaming, in eflect reduces the diameter of the nozzle 63 and nozzle orifice 63a, increasing the pressure of the fluid jet formed. It is this phenomenon which is believed to cause the attachment point of the jet along the wall 67 to move downd steam from the nozzle causing increased impingement upon the splitter 64 when an acoustic signal is applied.

The embodiment shown in FIGS. 6 and '7 isin most respects similar to that described and shown in connection with PEG. 5. The device 79 has a fluid power input '72, a power nozzle 73, and output channels and 76 separated by a splitter The principal dit erence between the embodiment shown in FIGS. 6 and 7 is that the acoustic driver 79 is located in the plane of the fluid jets two dimensional existence, rather than across the narrow dimension of the fluid jet. The operation of this embodiment is substantially identical to that shown in FIG. 5, the plane in which the acoustic signal is coupled to the fluid being the only change, and this does not change the operation of the device.

it will be apparent that the embodiments shown are only exemplary and that various modifications can be made in construction and arrangement within the scope of the invention as defined in the appended claims.

I claim as my invention:

ii. A fluid control device comprising:

(a) nozzle means for producing a fluid power jet,

(b) a plurality of output channels downstream of said nozzle means for receiving said jet, and

(c) means for controlling the position of said jet between said plurality of output channels including means for producing acoustic signals upstream of said nozzle means.

2. The fluid control device according to claim 1 wherein said acoustic signal producing means includes an elec trically energized transducer.

3. An acoustically controlled fluid jet device comprismg:

(a) nozzle means for forming a power jet along an axis,

(b) first and second output channels downstream of said nozzle means for receiving said power jet,

(0) a boundary wall intermediate said nozzle means and one of said output channels,

(d) means for biasing said power jet to lock-on to said boundary wall, and

(e) acoustic signal producing means upstream of said nozzle means for controlling the point of attachment of said power jet on said boundary wall, whereby (f) the presence of an acoustic signal changes said attachment point thereby altering the ditferential pressure between said output channels.

4. The acoustic controlled fluid jet device according to claim 3 wherein said acoustic signal producing means includes an electrically powered acoustic transducer.

5. The fluid jet device according to claim 4 wherein said transducer is positioned transverse said axis of said nozzle means.

6. The fluid jet device according to claim 4 wherein said transducer is positioned parallel to said nozzle axis.

References Cited by the Examiner UNITED STATES PATENTS 1,205,530 11/1916 Hall 13781.5 3,071,154 1/1963 Cargill et al. 137-815 3,144,037 8/1964 Cargill et a1. 13781.5 3,168,897 2/1965 Adams et a1. 13781.5 3,182,686 5/1965 Zilberfarb 13781.5 3,266,511 8/1966 Turick 13781.5 3,269,419 8/1966 Dexter 137-81.5

M. CARY NELSON, Primary Examiner.

W. R. CLINE, Assistant Examiner. 

1. A FLUID CONTROL DEVICE COMPRISING: (A) NOZZLE MEANS FOR PRODUCING A FLUID POWER JET, (B) A PLURALITY OF OUTPUT CHANNELS DOWNSTREAM OF SAID NOZZLE MEANS FOR RECEIVING SAID JET, AND (C) MEANS FOR CONTROLLING THE POSITION OF SAID JET BETWEEN SAID PLURALITY OF OUTPUT CHANNELS INCLUDING MEANS FOR PRODUCING ACOUSTIC SIGNALS UPSTREAM OF SAID NOZZLE MEANS. 